Allied Telesis AT-S63 - Manual (Page 134)

Chapter 7: Static and LACP Port Trunks
134 Section I: Basic Features
determine the maximum number of active ports the device can support
in a trunk. If the number is less than eight, the maximum number for
the AT-9400 Series switch, you should probably assign it a higher
system LACP priority than the AT-9400 Series switch. If it is more than
eight, assign the AT-9400 Series switch the higher priority. This can
avoid a possible conflict between the devices if some ports are placed
in the standby mode when the devices create the trunk. For
background information, refer to “LACP System Priority” on page 131.
ˆ LACPDU packets are transmitted as untagged packets.
Load Distribution
Methods
This section discusses the load distribution methods. It applies to both
static and LACP port trunks.
One of the steps to creating a static or LACP port trunk is the selection of
a load distribution method. This step determines how the switch distributes
the traffic load across the ports in the trunk. The AT-S63 management
software offers the following load distribution methods:
ˆ Source MAC Address (Layer 2)
ˆ Destination MAC Address (Layer 2)
ˆ Source MAC Address / Destination MAC Address (Layer 2)
ˆ Source IP Address (Layer 3)
ˆ Destination IP Address (Layer 3)
ˆ Source IP Address / Destination IP Address (Layer 3)
The load distribution methods examine the last three bits of a packet’s
MAC or IP address and compare the bits against mappings assigned to
the ports in the trunk. The port mapped to the matching bits is selected as
the transmission port for the packet.
In cases where you select a load distribution that employs either a source
or destination address but not both, only the last three bits of the
designated address are used in selecting a transmission port in a trunk. If
you select one of the two load distribution methods that employs both
source and destination addresses, port selection is achieved through an
XOR operation of the last three bits of both addresses.
As an example, assume you created a static or LACP aggregate trunk of
Ports 7 to 14 on a switch. The table below shows the mappings of the
switch ports to the possible values of the last three bits of a MAC or IP
address.
Last 3 Bits 000
(0) 001
(1) 010
(2) 011
(3) 100
(4) 101
(5) 110
(6) 111
(7)
Trunk Ports 7 8 9 10 11 12 13 14